ABSTRACTS 371 On the rheology of foams and highly concen- trated emulsions H.M. Princen, Ph.D., Exxon Research and Engi- neering Company, P.O. Box 45, Linden, NJ 07036. Expressions are derived for certain theological properties, such as the stress vs. strain relationship, yield stress and shear modulus, of monodisperse foams and highly concentrated emulsions for the model of infinitely long cylindrical drops (or bub- bles). The variables considered are the volume fraction of the dispersed phase, the drop radi-us, the interfacial tension, the thickness of the films sepa- rating adjacent drops, and the films' associated contact angle. Both the yield stress and the shear modulus are proportional to the interfacial tension and inversely proportional to the drop radius. The yield stress increases sharply with increasing vol- ume fraction, while the shear modulus varies as its square ro, ot. The effect of a finite contact angle, 0, is to decrease the shear modulus and in most cases, to increase the yield stress. Finally, the effect of a finite film thickness is always to increase both the yield stress and the shear modulus. Real emulsions and foams are expected to behave similarly, at least in a qualitative sense. Experimental evidence is provided. The application of rheology to cosmetic and pharmaceutical systems Nagin K. Patel, Ph.D., Anthony J. Cutie, Ph.D., Arnold and Marie Schwartz College of Pharmacy and Health Sciences, 75 DeKalb Avenue, Brooklyn, NY 11201. The cosmetic and pharmaceutical industry has recognized the importance of rheological assess- ments and product characterizations in solving some of the formulation problems (e.g., product texture, flow characteristics, and physical stability associated with suspensions, emulsions, and semi- solids). This paper examines some of the method- ologies and instrumentation presently used within these industries to characterize the structure of these rather complex heterogenous systems. The usefulness of rheograms is demonstrated in terms of formulating new products or reformulating existing products. Rheograms illustrating such sub- jects as the effect of various cellulose derivatives added, the effects of aging, and the addition of viscosity modifiers are presented, as well as specific delivery systems including methylcellulose gels, antacid suspensions, creams, and semi-solids lip- sticks. The application of such data necessary to the formulation design, scale-up operation, stability, texture, and final use of the cosmetic pharmaceuti- cal product is illustrated. SPECIAL TOPICS IN METHODOLOGY Skin irritation and DNA damaging qualities of cosmetics Shigeru Yamamoto, M.D., TBC-America, 606 N. Larchmont Blvd., Los Angeles, CA 90004. In Japan, reports of injuries due to cosmetics in 1981 markedly increased 162% from the previous year. The cosmetics that were the cause of the complaints were mostly products of major manu- facturers that had been thoroughly tested. Despite the fact that the cause is sometimes the consumer's fault, the number of complaints indicate that the cosmetics are a contributing cause. If there is a causal effect from the products, it seems clear that present skin irritation tests are not sufficient for determining the skin irritation properties of cos- metics, and that some problems relating to skin irritation are undetected. During dermatological diagnosis of patients having skin irritations caused by contact with cosmetics, it was found that cosmetics with a high irritation potential very often also caused damage to the DNA of Bacillus coli. Those cosmetics showing strong reactions in patch tests had the most DNA-damaging properties. Translating this finding to cosmetic formulation suggests that the aim should be to make cosmetics with low DNA-damaging properties. This means that cosmetics with less irritation potential can be made more economically, easily, and quickly than before. The DNA-damage test should be incorpo- rated into cosmetic irritation test protocols as a more effective method than the patch tests and animal studies used at present. ,'.vaiuaun• cleaning toothbrush designs and textures Samuel L. Yankell, Ph.D., P. Nygaard-Ostby, D.D.S., University of Pennsylvania School of Den- tal Medicine, 4001 Spruce Street, Philadelphia, PA 19104. Cleanliness of the oral cavity is imperative for cosmetic appearance and dental health, and the toothbrush is the main aid for this purpose. There is a need for better laboratory and clinical assessment of toothbrush efficiency. The purpose of this study is to evaluate the efficiency of toothbrushes of different designs and textures. An apparatus was utilized that simulates horizontal and vertical brush- ing movements at various pressures on anterior and posterior shaped teeth. Cleaning efficiency was scored by measuring the accessibility between the

372 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS simulated teeth. Fourteen different brushes with varying designs and textures were evaluated. Cleaning efficiency improved with softer texture and increasing pressure. At similar bristle textures, V-shaped brushes had significantly better cleaning efficiency than straight multitufted toothbrushes. Two new clinical studies supported these laboratory findings. Transepidermal moisture loss iv: the effect of moisturizers on dry skin on the back of the hand Michael Cheney, G. Berube, F. Tranner, P. Miner, Chesebrough-Pond's Inc., Trumbull Industrial Park, Trumbull, CT 06611. A series of studies were conducted to evaluate the difference in transepidermal water loss (TEWL) between normal skin, dry skin, and dry skin treated with different moisturizers. The measurement sys- tem uses a carrier gas to "pick up" moisture from the back of the hand (as opposed to the volar forearm) and deliver it to a dew point analyzer. The carrier gas has been "humidified" to 20% RH, which is more reflective of the "in-use" conditions of moisturizing products. Data from three studies conducted over the last three years showed that the TEWL rates for dry skin (soap enhanced) increase significantly over baseline (normal skin) readings, while product application reduces the TEWL closer to pretreatment values. Supportive data including scanning electron microscope photographs, instru- mental assessments, and visual scoring will be included. The importance of this protocol in direct- ing the formulation and evaluation of skin care products is discussed. Set relaxation of human hair Penelope Diaz, Michael Y.M. Won& Clairol Research Laboratories, 2 Blachley Road, Stamford, CT 06902. Although hair can be effectively set by water, heat, or both, such temporary sets do relax over time. It has been found that the set relaxation process can be adequately described, over a wide range of humidity, by the expression Y = aT b, where Y is the amount of set remaining after an exposure to humidity for a period of time T, and a and b are constants. In fact, the integrated form of this equation can conveniently be used to compare the effectiveness of hair sprays, setting parameters, etc. SYMPOSIUM ON COSMETIC EVALUATION Evaluation of hand and body lotions: correla- tion of objective and subjective responses John P. McCook, Gene R. Berube, Chesebrough- Pond's Inc., Trumbull Industrial Park, Trumbull, CT 06611. Various testing techniques or methodologies are used in the development, screening, selection, and comparative testing of hand and body lotions. These test methods may include in-vitro instru- mental analysis or in-vivo testing. In-vivo human testing can involve laboratory panels, home place- ment, or consumer panels, as well as clinical testing. Measurement of the overall performance of hand and body lotions for relief of dry skin symptoms as well as measurement of aesthetic qualities and consumer acceptance can be accomplished via panel testing and clinical testing. Subjective responses from panelists or consumers as well as objective measurements by trained judges or clini- cians are used to determine efficacy, product accep- tance, and overall performance. This paper presents the results of various panel tests and clinical evalua- tions designed to measure product efficacy and consumer acceptance. Through graphic representa- tion, objective and subjective data are given for various hand and body lotion products. Relative value and correlation of subjective and objective responses are discussed. Results show good corre- lation of subjective and objective assessment of hand and body lotion performance. Radiotracer and autoradiographic studies of cosmetic products Raymond L. Sheath, Ph.D., J.G. Gould, H.T. Fox, The Gillette Company, Gillette Park, Boston, MA 02106. The classic subjective and objective methods are and may continue to be the primary means of evaluating hair care products. However, with increasing frequency, newer techniques are appearing which can provide more detailed infor- mation concerning specific interactions of cos- metic products with hair. During the last twenty years, radioisotopes have been widely used for laboratory evaluation of hair care products. These standard radiotracer techniques have recently been extended to include autoradiographic studies which permit direct visualization of the sites of interaction of cosmetic products with hair fibers. This combination of techniques has proven to be a very accurate measure of substantivity, penetration, and reactivity and also may provide important insights into the mechanism by which products deliver the desired benefit. Numerous cosmetic treatments, including conditioners, have been stud- ied. The results of several conditioner studies provided the basic claim support for a line of products. These and several other radiotracer and autoradiographic studies are discussed.